The present invention relates to a fully jacketed centrifuge with a helical conveyor for separating mixtures of solids and liquid, in which the mixture of solids and liquid is fed into the conveyor through an inlet space that has an access and some or all of the centrifuged solids are extracted through extraction apertures located below the surface of the liquid in the jacket of the drum.
A centrifuge of this type is known, for example, from German OS No. 2 930 581. One drawback of this known centrifuge is that a constant volume flows out of the apertures on account of their diameter. Depending, therefore, on the amount of solids in the centrifuge access, the solids will flow out of the apertures at a varying consistency or the centrifuge must be stopped so that the diameter of the apertures can be adjusted to the volume of solids. When the volume of solids is very low however, the apertures must be very small and will easily clog up.
German OS No. 2 942 451 accordingly proposes controls that are provided with a mechanism to open and close the apertures. The controls consist of a baffle that is mounted on the helical portion of the conveyor and is in operating communication with the apertures. The baffle is designed so that the difference in rotations per minute between the helix and the drum jacket will alternately block off and release the apertures. Controls of this type are very expensive to manufacture and necessitate a separate drive mechanism. It is not sufficient to vary the differential speed in order to control the volume extracted. The differential speed must, rather, be irregular, more rapid when the apertures are closed and slower when they are open or vice versa. Controls that are so complicated, however, are not appropriate in practice. Furthermore, when the solids are of the nature of a paste, it is impossible for the baffle to block off the apertures, and the controls are of limited application.